The present invention relates to a motor drive control such as a safety or protection apparatus in an automatic opening/closing mechanism of a window, for example, for an automobile (hereinafter referred to as a power window).
With progress in the development of integrated circuit technology, electronic control apparatuses utilizing integrated circuit components are widely used in every corner of many industrial fields, and such electronic control apparatuses are also employed for engine control, display of vehicle speed and opening or closing of windows of vehicles, particularly of automobiles.
A power window system for automatically opening and closing the windows of vehicles from the driver's seat is already widely put into practical use. In such a power window system, the window is opended or closed by the operation of a switch. If a driver's hand is caught by the window during the closing operation, said window must be opened by opening the window through operating the switch. However, in order to prevent an accident to a child by mischief, it is required that the window be automatically opened by detecting that a foreign object is caught by the window.
Therefore, a safety apparatus for reversely controling the operation of a power window to the opening mode when it detects an excessive load applied on the power window in the closing mode is under investigation at present.
In such a load detection method of this safety apparatus, it is essential to individually detect factors such as the road condition when a car is running, wind pressure applied on the window, change of load due to the play of mechanical parts and change of load due to the catching of a substance or a hand, etc.
If a hand is caught, it must be detected as quickly as possible. This safety apparatus is generally controlled by a micro-computer and therefore it is desirable that a control algorithm or process which alleviates the processing load for the microcomputer as much as possible be developed.
Moreover, such safety apparatus is required to always assure and guarantee the safety of operation even under any operating condition.
For example, it is not permissable that the safety operation be lost by a failure even if such failure occurs at a part of the safety apparatus. Therefore, advent of a safety apparatus which ensures safe operation even if a major component fails has long been desired.